The present invention relates to color signal processing in a TV receiver and more particularly to adaptively filtering the color signals in accordance with the bandwidth of the current color signal averaged over a short interval. In so doing the filter bandwidth is continuously adjusted resulting in an average bandwidth significantly less than the value required of a fixed filter to pass the higher frequency color signal components thereby enhancing the signal-to-noise ratio of the color signal.
In standard analog TV receiver design color signals are filtered to eliminate out-of-band noise. The bandwidth of such filters is generally a compromise design with the view of achieving good transient response while at the same time suppressing noise to the fullest extent commensurate therewith. If the filter bandwidth were instantaneously varied in accordance with the spectral content of the current signal both functions could be realized without the compromise. In the receiver the color signals are ultimately combined with the luminance signal to generate R, G and B signals to drive the kinescope. It is therefore imperative that the color signal filter introduce substantially no differential phase delay between the color and luminance signals. It is not presently practical to design an adaptive analog filter which does not introduce differential phase delay between the color and luminance signals that ultimately produces smeared or blurred images when reproduced on the TV screen.
It is however presently practical to process video signals with digital techiques. Further, if finite impulse response or FIR filters are utilized to perform the filter functions, they may be programmed for adaptively adjusting bandwidths and amplitude response without introducing differential phase delay.